CN112881529B - Method and system for damage monitoring of composite material structures based on laser piezoelectric technology - Google Patents

Abstract

The invention provides a composite material structure damage monitoring method based on laser piezoelectric technology, which includes receiving the signal formed when the laser head scans all the scanning points on the composite material board globally each time; and processing the signal received each time , to obtain the time delay of the direct wave from each array element to each scanning point, and combine the time delay of the direct wave from the same scanning point to each array element, calculate in the preset steering vector formula, and obtain the steering vector array of each scanning point ; The steering vectors in the steering vector array of each scanning point are represented by the real unit, so that the steering vector array of each scanning point is a corresponding column of vectors, and the Euclidean distance between the column vectors is calculated, and the Euclidean distance is obtained The area between the two scanning points with the smallest distance calculation value is further output as the damage monitoring area. By implementing the invention, damage monitoring and impact position estimation can be realized without prior measurement and calculation of material parameters of the material structure.

Description

Method and system for damage monitoring of composite material structures based on laser piezoelectric technology

technical field

The invention relates to the technical field of composite material structure health monitoring, in particular to a composite material structure damage monitoring method and system based on laser piezoelectric technology.

Background technique

Composite materials are widely used in industry due to their light weight, high strength, and other desirable mechanical properties. However, composite materials are prone to defects, which reduce reliability during application and threaten the safety performance of the structure. At the same time, considering that the structural parameters of composite materials used in industry are different, large and complex structures will use composite materials with different material parameters to achieve different functions of the structure. Therefore, damage monitoring for composite structures with different material parameters is very important.

In recent years, there have been many methods for damage monitoring of composite structures, and the use of various technologies has promoted the development of structural monitoring technology. Composite material structures with known material parameters can be easily simulated by using finite element analysis technology. In practice, a variety of effective damage monitoring technologies can also be adopted, such as infrared imaging, acoustic emission, eddy current, etc., combined with positioning algorithms. Estimate the location of the damage.

However, for composite structures with unknown material parameters, it is necessary to conduct experiments to obtain material parameters first, and then calculate the material parameters of the structure before performing damage monitoring. Therefore, it is necessary to propose an online damage monitoring method for composite structures with unknown material parameters, which can realize damage monitoring and impact position estimation without prior calculation of the material parameters of the material structure.

Contents of the invention

The technical problem to be solved by the embodiments of the present invention is to provide a composite material structure damage monitoring method and system based on laser piezoelectric technology, which can realize damage monitoring and impact position estimation without prior calculation of material parameters of the material structure.

In order to solve the above technical problems, the embodiment of the present invention provides a composite material structure damage monitoring method based on laser piezoelectric technology, which is used on composite material plates with unknown material parameters, and the composite material plates are preset with linear array piezoelectric A sensor and a plurality of scanning points distributed around the linear array piezoelectric sensor, the method includes the following steps:

S1. Receive the signal formed when the laser head globally scans all scanning points on the composite material board; wherein, the number of global scans of the laser head corresponds to the total number of array elements in the linear piezoelectric sensor, and the Each global scan of the laser head is triggered when a corresponding array element in the linear array piezoelectric sensor is excited by a Lamb wave signal;

S2. Process the signal formed during the global scanning of the laser head each time to obtain the time delay of the direct wave from each array element to each scanning point, and combine the time delay of the direct wave from the same scanning point to each array element , calculate in the preset steering vector formula to obtain the steering vector matrix of each scanning point;

S3. The steering vectors in the steering vector arrays of each scanning point are characterized by the real part unit, so that the steering vector arrays of each scanning point are corresponding column vectors, and the Euclidean distance between the column vectors is calculated, and the Euclidean distance is obtained. The area between the two scanning points with the smallest calculated value of the distance, and further output the acquired area as the damage monitoring area.

Wherein, the method further includes:

Collect the array signal of the damage point to be located to obtain the time delay of the direct arrival wave from the damage point to be located to each array element, and perform calculation in the preset steering vector formula to obtain the steering vector array of the damage point to be located, and further The steering vector array of the damage point to be located is compared with the steering vector array of each scanning point, and in the damage monitoring area, the position of the scanning point closest to the damage point to be located is determined as the position of the damage point to be located.

Among them, the Lamb wave signal excitation for each array element is realized by using the amplifier to amplify the corresponding array element after calling the 50KHz Lamb wave signal function through the function generator.

其中，Wherein, the preset steering vector formula is

in,

且x_k(k＝1，2，...，M)为第k个阵元的位置，c为光速，M为阵元总数；τ_ki为第i个扫描点至第k个阵元的直达波时间延迟。a(θ _i ) is the steering vector of the i-th scanning point; θ _i (i=1, 2,..., N) is the azimuth of the i-th scanning point, and the azimuth represents the relationship with the y-axis Angle, and N is the total number of scanning points;

And x _k (k=1, 2, ..., M) is the position of the kth array element, c is the speed of light, M is the total number of array elements; τ _ki is the distance from the i-th scanning point to the k-th array element Direct wave time delay.

The embodiment of the present invention also provides a composite material structure damage monitoring system based on laser piezoelectric technology, which is used on a composite material board with unknown material parameters, and the composite material board is preset with a linear array piezoelectric sensor and surrounding the Multiple scanning points distributed around the linear array piezoelectric sensor, including:

The signal receiving unit is used to receive the signal formed when the laser head globally scans all the scanning points on the composite material board; wherein, the number of global scans of the laser head is equal to the total number of array elements in the linear piezoelectric sensor Corresponding, and each global scan of the laser head is triggered based on the excitation of a corresponding array element in the linear piezoelectric sensor by a Lamb wave signal;

The guide vector array acquisition unit is used to process the signal formed during the global scanning of the laser head each time, so as to obtain the time delay of the direct arrival wave from each array element to each scanning point, and combine the same scanning point to each array The direct wave time delay of the element is calculated in the preset steering vector formula to obtain the steering vector array of each scanning point;

The damage monitoring area acquisition unit is used to characterize the steering vectors in the steering vector array of each scanning point with a real part unit, so that the steering vector array of each scanning point is a corresponding column of vectors, and calculate the Euclidean value between the column vectors and obtain the area between the two scanning points with the smallest Euclidean distance calculation value, and further output the acquired area as the damage monitoring area.

Among them, also include:

The damage point position estimation unit is used to collect the array signal of the damage point to be positioned to obtain the time delay of the direct arrival wave from the damage point to be positioned to each array element, and perform calculation in the preset steering vector formula to obtain the The steering vector array of the damage point, further compare the steering vector array of the damage point to be located with the steering vector array of each scanning point, in the damage monitoring area, determine the position of the scanning point closest to the damage point to be located as undetermined location of the damage point.

其中，Wherein, the preset steering vector formula is

in,

且x_k(k＝1，2，...，M)为第k个阵元的位置，c为光速，M为阵元总数；τ_ki为第i个扫描点至第k个阵元的直达波时间延迟。a(θ _i ) is the steering vector of the i-th scanning point; θ _i (i=1, 2,..., N) is the azimuth of the i-th scanning point, and the azimuth represents the relationship with the y-axis Angle, and N is the total number of scanning points;

And x _k (k=1, 2, ..., M) is the position of the kth array element, c is the speed of light, M is the total number of array elements; τ _ki is the distance from the i-th scanning point to the k-th array element Direct wave time delay.

Implementing the embodiment of the present invention has the following beneficial effects:

The present invention utilizes laser piezoelectric technology to obtain the Lamb wave propagation inside the composite material structure, and obtains the steering vector array of each scanning point to all array elements with the signal formed by the laser head when each array element is excited, and according to The Euclidean distance calculation value of the steering vector array is used to represent the difference, and the damage monitoring area and impact position are estimated, so that damage monitoring and impact position estimation can be realized without prior calculation of the material parameters of the material structure.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, obtaining other drawings based on these drawings still belongs to the scope of the present invention without any creative effort.

Fig. 1 is a flow chart of a method for monitoring damage of a composite material structure based on laser piezoelectric technology provided by an embodiment of the present invention;

Fig. 2 is a layout diagram of the laser experimental device set up for the damage monitoring of the composite material structure in the damage monitoring method of the composite material structure based on the laser piezoelectric technology provided by the embodiment of the present invention;

Fig. 3 is a schematic diagram of the non-differential time delay of the direct path between the scanning point and the array element in the damage monitoring method for composite material structure based on laser piezoelectric technology provided by the embodiment of the present invention;

Fig. 4 is a schematic structural diagram of a composite material structure damage monitoring system based on laser piezoelectric technology provided by an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

The inventors found that when the piezoelectric sensor is used to excite the composite material structure, and the laser monitors the propagation of the Lamb wave in the plate by non-contact, the scattering phenomenon will occur when the wave propagates to the damaged position. Therefore, according to the Lamb wave scattering signal collected by the laser, after the signal features are extracted by signal processing technology, the damage location can be estimated in combination with the positioning algorithm. Therefore, based on the above theory, the inventors proposed a method for monitoring damage of composite material structures based on laser piezoelectric technology.

As shown in Figure 1, in the embodiment of the present invention, the inventor proposes a method for monitoring composite material structure damage based on laser piezoelectric technology, which is used on a composite material plate with unknown material parameters, and the composite material plate The preset linear array piezoelectric sensor and multiple scanning points distributed around the linear array piezoelectric sensor include the following steps:

Step S1, receiving the signal formed when the laser head globally scans all scanning points on the composite material board each time; wherein, the number of global scans of the laser head corresponds to the total number of array elements in the linear piezoelectric sensor, and Each global scan of the laser head is triggered based on the excitation of a corresponding array element in the linear piezoelectric sensor by a Lamb wave signal;

The specific process is, for a composite material board with unknown parameters, set up the experimental device as shown in Figure 2, arrange a line array sensor with M (such as 7) array elements on the composite material board, and use the function generator to call 50KHz After the Lamb wave signal function, it is amplified by the amplifier to excite each array element separately, and each array element is excited, and the laser head scans all the preset scanning points (N) once. After M times of scanning, the global scanning information (including N scanning point signals) obtained by different excitation array elements can be obtained.

Step S2. Process the signal formed during the global scanning of the laser head each time to obtain the time delay of the direct wave from each array element to each scanning point, and combine the direct wave time from the same scanning point to each array element Delay, calculated in the preset steering vector formula to obtain the steering vector matrix of each scanning point;

The specific process is as follows. First, it is considered that the steering vector represents the information of the signal in space, including all the information of the spatial phase of the signal, including the time delay response. In view of the fact that the time delay on the direct path does not produce a difference (as shown in Figure 3), but the time delay for the signal scattering (that is, the location of the damage) will produce a deviation, so it can be considered that the time delay for the direct wave on the signal propagation path It is consistent with the information received by the previous impact point excitation array sensor.

At this time, the received signal formed during global scanning of the laser head is processed each time to obtain the time delay of the direct wave from each array element to each scanning point.

Secondly, for the steering vector, formula (1) can be used to express:

a(ω ₀ )＝exp(-jω ₀ τ _ki ) (1)

c为光速，λ为波长。In the formula, k=1...M; i=1...N;

c is the speed of light, and λ is the wavelength.

For a linear array, the mutual delay expression between array elements is shown in formula (2):

In the formula, τ _ki is the direct wave time delay from the i-th scanning point to the k-th array element; x _k (k=1, 2,...,M)x _k (k=1, 2,... , M) is the position of the k-th array element; the signal incident parameter is assumed to be θ _i (i=1, 2,..., N) is the azimuth of the i-th scanning point, and the azimuth represents the relationship with y The included angle of the axis (that is, the included angle with the line array normal).

Therefore, formula (1) can be transformed into a steering vector formula related to the azimuth angle θ based on formula (2). As shown in formula (3):

Among them, a(θ _i ) is the steering vector of the i-th scanning point.

Mathematically, the wavelength and azimuth are calculated, and the steering vector of the corresponding scanning point can be obtained. In the laser piezoelectric array method, since there is no difference in the time delay of the direct wave on the direct path, the time delay of the direct wave at each scanning point obtained by exciting the M array elements in the linear array can be used as the steering vector τ _ki , so as to obtain the steering vector array in the laser piezoelectric array method.

It can be seen that the time delay of the direct wave from the same scanning point to each array element is substituted into the steering vector formula (3) for calculation, and the steering vector array of each scanning point is obtained.

Step S3, characterize the steering vectors in the steering vector array of each scanning point with the real unit, so that the steering vector array of each scanning point is a corresponding column of vectors, and calculate the Euclidean distance between the column vectors, and obtain The area between the two scanning points with the smallest Euclidean distance calculation value is further output as the damage monitoring area.

The specific process is that after obtaining the steering vector arrays of all scanning points, since the steering vector is a quantity with an imaginary unit, the real part of the steering vector with the imaginary unit is taken during the comparison process. Therefore, each scanning point can be represented by the real part unit in the steering vector excited by the point to different array elements. Since it is a linear array, it can be described as a column of vectors. By taking the Euclidean distance between each column vector, the difference information of the steering vector between different scanning points can be obtained, and based on the difference information, the array signal of the damage point to be located collected by the laser piezoelectric technology can be monitored and estimated Impact position.

Therefore, the steering vectors in the steering vector array of each scanning point are all characterized by the real part unit, so that the steering vector array of each scanning point is a corresponding column of vectors, and the Euclidean distance between the column vectors is calculated, and further can be The area between the two scanning points with the smallest Euclidean distance calculation value is obtained as the damage monitoring area.

In the embodiment of the present invention, the smaller the difference between the steering vectors is, the closer the real part unit features of the steering vectors are, making it more likely that the impact position of the damage point to be located is near the position of the scanning point. Accordingly, the method further includes:

Collect the array signal of the damage point to be located to obtain the time delay of the direct arrival wave from the damage point to be located to each array element, and perform calculation in the preset steering vector formula to obtain the steering vector array of the damage point to be located, and further The steering vector array of the damage point to be located is compared with the steering vector array of each scanning point, and in the damage monitoring area, the position of the scanning point closest to the damage point to be located is determined as the position of the damage point to be located.

Based on Figure 2 and Figure 3, the application scenario of a composite material structure damage monitoring method based on laser piezoelectric technology proposed in the embodiment of the present invention is further explained:

Take a composite material structural plate with unknown material parameters as an example, the size is 300mm×300mm×2mm, and the layup information and fiber direction are unknown. The composite material plate is clamped by the clamping device, and it is placed firmly and upright. Paste a 7-element sensor array, connect the laser piezoelectric device through Figure 2, make the laser beam hit the material plate vertically, adjust the laser focus, distance, set the reference point and other series of operations in the user interface, and slightly move the material Board, observe whether there is a signal image generated in the laser piezoelectric user interface, and ensure the normal operation of the laser piezoelectric device. The main steps include the following parts:

(1) Piezoelectric excitation: After setting the relevant laser parameters, the 50KHz Lamb wave signal function is called in the function generator, and after being amplified by the amplifier, it acts on the piezoelectric sensor in the center of the material plate. excitation;

(2) Laser scanning: After the piezoelectric sheet is excited, the laser beam starts to scan in an orderly manner according to the preset scanning points. It is necessary to re-scan once for different sensor excitations, so in this case, the laser beam scans 7 times in total;

(3) Acquisition of the steering vector array: After processing the signal scanned by the laser, the time delay of each sensor receiving signal at the same spatial position is obtained, and the time delay is brought into the steering vector formula to obtain each scanning point The steering vector array;

(4) Acquisition of the damage monitoring area: the steering vector is an imaginary number with an imaginary unit, and the real part features of all steering vectors are taken during processing. The steering vector of each scanning point can be represented by a vector described by the real unit. By taking the Euclidean distance between the vectors, the difference information of the steering vectors between different scanning points can be obtained. The smaller the difference, the closer the real part unit features of the steering vectors are, and the greater the possibility that the impact position is near the scanning point. According to the difference information, the fault source signal collected by laser piezoelectric technology can be monitored and the impact position can be estimated.

As shown in Figure 4, in the embodiment of the present invention, a composite material structure damage monitoring system based on laser piezoelectric technology is provided, which is used on a composite material board with unknown material parameters, and the composite material board is preset with a cable An array of piezoelectric sensors and a plurality of scanning points distributed around the linear array of piezoelectric sensors, including:

The signal receiving unit 110 is used to receive the signal formed when the laser head globally scans all the scanning points on the composite material board; wherein, the number of global scans of the laser head is related to the total number of array elements in the linear piezoelectric sensor Corresponding, and each global scan of the laser head is triggered based on the excitation of a corresponding array element in the linear piezoelectric sensor by a Lamb wave signal;

The steering vector array acquisition unit 120 is used to process the signal formed during the global scanning of the laser head each time, so as to obtain the time delay of the direct arrival wave from each array element to each scanning point, and combine the same scanning point to each scanning point. The time delay of the direct arrival wave of the array element is calculated in the preset steering vector formula to obtain the steering vector array of each scanning point;

The damage monitoring area acquisition unit 130 is used to characterize the steering vectors in the steering vector array of each scanning point with the real part unit, so that the steering vector array of each scanning point is a corresponding column of vectors, and calculate the relationship between the column vectors Euclidean distance, and obtain the area between the two scanning points with the smallest Euclidean distance calculation value, and further output the obtained area as the damage monitoring area.

Among them, also include:

The damage point position estimation unit is used to collect the array signal of the damage point to be positioned to obtain the time delay of the direct arrival wave from the damage point to be positioned to each array element, and perform calculation in the preset steering vector formula to obtain the The steering vector array of the damage point, further compare the steering vector array of the damage point to be located with the steering vector array of each scanning point, in the damage monitoring area, determine the position of the scanning point closest to the damage point to be located as undetermined location of the damage point.

其中，Wherein, the preset steering vector formula is

in,

且x_k(k＝1，2，...，M)为第k个阵元的位置，c为光速，M为阵元总数；τ_ki为第i个扫描点至第k个阵元的直达波时间延迟。a(θ _i ) is the steering vector of the i-th scanning point; θ _i (i=1, 2,..., N) is the azimuth of the i-th scanning point, and the azimuth represents the relationship with the y-axis Angle, and N is the total number of scanning points;

And x _k (k=1, 2, ..., M) is the position of the kth array element, c is the speed of light, M is the total number of array elements; τ _ki is the distance from the i-th scanning point to the k-th array element Direct wave time delay.

Implementing the embodiment of the present invention has the following beneficial effects:

The present invention utilizes laser piezoelectric technology to obtain the Lamb wave propagation inside the composite material structure, and obtains the steering vector array of each scanning point to all array elements with the signal formed by the laser head when each array element is excited, and according to The Euclidean distance calculation value of the steering vector array is used to represent the difference, and the damage monitoring area and impact position are estimated, so that damage monitoring and impact position estimation can be realized without prior calculation of the material parameters of the material structure.

It is worth noting that in the above system embodiments, the units included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be realized; in addition, the specific names of each functional unit It is only for the convenience of distinguishing each other, and is not used to limit the protection scope of the present invention.

Those of ordinary skill in the art can understand that all or part of the steps in the method of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage Media such as ROM/RAM, magnetic disk, optical disk, etc.

The above disclosure is only a preferred embodiment of the present invention, which certainly cannot limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims (7)

1. A composite material structure damage monitoring method based on a laser piezoelectric technology is characterized in that the method is used for a composite material plate with unknown material parameters, a linear array piezoelectric sensor and a plurality of scanning points distributed around the linear array piezoelectric sensor are preset on the composite material plate, and the method comprises the following steps:

s1, receiving signals formed by a laser head when the laser head globally scans all scanning points on the composite material plate every time; the laser head global scanning times correspond to the total number of array elements in the linear array piezoelectric sensor, and each global scanning of the laser head is triggered on the basis that a corresponding array element in the linear array piezoelectric sensor is excited by a Lamb wave signal;

s2, processing signals formed during global scanning of the laser head received each time to obtain the time delay of the direct wave from each array element to each scanning point, and calculating in a preset guide vector formula by combining the time delay of the direct wave from the same scanning point to each array element to obtain a guide vector array of each scanning point;

and S3, representing the guide vectors in the guide vector array of each scanning point by a real part unit, so that the guide vector array of each scanning point is a corresponding column of vectors, calculating the Euclidean distance between the columns of vectors, acquiring the area between two scanning points with the minimum calculated Euclidean distance value, and further outputting the acquired area as a damage monitoring area.

2. A method for damage monitoring of a composite structure based on laser piezo technology according to claim 1, characterized in that the method further comprises:

collecting array signals of the damage points to be positioned to obtain the direct wave time delay from the damage points to be positioned to each array element, calculating in the preset guide vector formula to obtain a guide vector array of the damage points to be positioned, further comparing the guide vector array of the damage points to be positioned with the guide vector array of each scanning point, and determining the position of the scanning point with the nearest distance from the damage points to be positioned as the position of the damage points to be positioned in the damage monitoring area.

3. The method for monitoring the structural damage of the composite material based on the laser piezoelectric technology as claimed in claim 1, wherein the Lamb wave signal excitation of each array element is realized by using a function generator to adjust a 50KHz Lamb wave signal function and then using an amplifier to amplify the corresponding array element.

4. The method for monitoring the structural damage of the composite material based on the laser piezoelectric technology as claimed in claim 1 or 2, wherein the preset guide vector formula is

Wherein, a (theta) _i ) A guide vector of an ith scanning point; theta _i (i =1,2.., N) is the azimuth angle of the ith scanning point, which represents the angle to the y-axis, N is the total number of scanning points, and λ is the wavelength;

and x _k (k =1,2.., M) is the position of the kth array element, c is the Lamb wave velocity, and M is the total number of array elements; tau is _ki The time delay of the direct wave from the ith scanning point to the kth array element.

5. A composite material structure damage monitoring system based on laser piezoelectric technology is characterized in that the system is used for a composite material plate with unknown material parameters, a linear array piezoelectric sensor and a plurality of scanning points distributed around the linear array piezoelectric sensor are preset on the composite material plate, and the system comprises:

the signal receiving unit is used for receiving signals formed by the laser head when the laser head globally scans all scanning points on the composite material plate every time; the laser head global scanning times correspond to the total number of array elements in the linear array piezoelectric sensor, and each global scanning of the laser head is triggered on the basis that a corresponding array element in the linear array piezoelectric sensor is excited by a Lamb wave signal;

the guide vector array obtaining unit is used for processing signals formed during the global scanning of the laser head received each time so as to obtain the time delay of the direct wave from each array element to each scanning point, and calculating in a preset guide vector formula by combining the time delay of the direct wave from the same scanning point to each array element to obtain a guide vector array of each scanning point;

and the damage monitoring area acquisition unit is used for representing the guide vectors in the guide vector array of each scanning point by a real part unit, so that the guide vector array of each scanning point is a corresponding column of vectors, calculating the Euclidean distance between the columns of vectors, acquiring an area between two scanning points with the minimum calculated Euclidean distance value, and further outputting the acquired area as a damage monitoring area.

6. A composite structure damage monitoring system based on laser-piezo technology according to claim 5, further comprising:

and the damage point position estimation unit is used for acquiring array signals of the damage point to be positioned so as to acquire the time delay of direct waves from the damage point to be positioned to each array element, calculating in the preset guide vector formula to obtain a guide vector array of the damage point to be positioned, further comparing the guide vector array of the damage point to be positioned with the guide vector array of each scanning point, and determining the position of the scanning point, which is closest to the damage point to be positioned, as the position of the damage point to be positioned in the damage monitoring area.

7. A composite structure damage monitoring system based on laser-piezo technology according to claim 5 or 6, characterized in that the preset steering vectorIs given by the formula

Wherein, a (theta) _i ) A guide vector of the ith scanning point; theta.theta. _i (i =1,2.., N) is the azimuth angle of the ith scanning point, which represents the angle to the y-axis, N is the total number of scanning points, and λ is the wavelength;

and x _k (k =1,2.., M) is the position of the kth array element, c is the Lamb wave velocity, and M is the total number of array elements; tau. _ki The time delay of the direct wave from the ith scanning point to the kth array element.

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